(1) Field of the Invention
The present invention relates to digital switching systems and more particularly to a pulse monitor circuit for use in such switching systems.
(2) Description of the Prior Art
Typical digital pulse monitor circuits require complex logic circuitry and are often unreliable and subject to race conditions. A recent advancement in the state of the art was disclosed by H. Ballentine in an article entitled "Clock-Activity Detector Uses One DIP", Electronic Design News, Jan. 5, 1980, page 156. However, this circuit is still relatively complex, and any detected failure signal is cleared when the monitored clock signal reappears. Some implementations of this circuit may also suffer from insufficient clear pulse widths.
Accordingly, it is the object of the present invention to provide a minimum component, highly reliable pulse monitor circuit, free of any potential race problems and resettable by an external clear signal or reappearance of the monitored pulse.